Ethylene interpolymers products are widely used in rotomolding applications to produce a wide variety of manufactured articles. Non-limiting examples of rotomolded articles include: toys, bins, containers, helmets, boats, large tanks. Such articles are produced using conventional rotomolding equipment, non-limiting examples include: clamshell machines, shuttle machines, swing arm machines, carousel machines and the like. There is a need to improve the stiffness of rotomolding articles, while maintaining or increasing the Environmental Stress Crack Resistance (ESCR). It is well known to those of ordinary experience in the art that the stiffness of a rotomolded article can be increased by increasing the density of the ethylene interpolymer; however, it is also well known that ESCR typically decreases as density increases.
Herein, ethylene interpolymer products are disclosed that can be fabricated into rotomolded parts that are stiffer and yet have equivalent or higher ESCR relative to comparative ethylene interpolymers. The ethylene interpolymer products disclosed were produced in a solution polymerization process, where catalyst components, solvent, monomers and hydrogen are fed under pressure to more than one reactor. For ethylene homo polymerization, or ethylene copolymerization, solution reactor temperatures can range from about 80° C. to about 300° C. while pressures generally range from about 3 MPag to about 45 MPag and the ethylene interpolymer produced remains dissolved in the solvent. The residence time of the solvent in the reactor is relatively short, for example, from about 1 second to about 20 minutes. The solution process can be operated under a wide range of process conditions that allow the production of a wide variety of ethylene interpolymers. Post reactor, the polymerization reaction is quenched to prevent further polymerization, by adding a catalyst deactivator, and passivated, by adding an acid scavenger. Once passivated, the polymer solution is forwarded to a polymer recovery operation where the ethylene interpolymer is separated from process solvent, unreacted residual ethylene and unreacted optional α-olefin(s).